Simplified Calculation of Pylon Top Displacement of Multi-Pylon Suspension Bridge

The long-span multi-pylon suspension bridge is the subject of growing interest. Under live load, the longitudinal deflection of the mid-pylon is an important control parameter for a multi-pylon suspension bridge design. It is important to establish a simplified method of calculating pylon deflection for the preliminary design and selection of a multi-pylon suspension bridge. Based on deflection theory and deformation compatibility condition, considering main cable horizontal constraints and the interaction among pylons and girders with the methods of equivalent stiffness and moment distribution, the simplified calculation formulas of pylon displacement at the top for three-, four-, and five-pylon suspension bridges are derived. The validity of the formulas are verified by model experiment, real bridge testing, and finite-element analysis. For a floating system, the error between the simplified formula and the finite element method is less than 10%, and that of the model experiment is within 25%. For a consolidation system, the error between the simplified formula and the finite element method is within 16%, and that of the real bridge testing is less than 11%. As the number of pylons increases, the simplified formulas tend to be less accurate.